Infrared audio systems are commonly used to transmit audio signals in environments in which radio frequency signals are impractical or not desired. The audio is modulated (e.g., FM modulation) for transmission, and the modulated signal is transmitted using one or more infrared light emitting diodes (LEDs) (also referred to herein as “LED emitters”). The LED emitters emit a modulated infrared light (hereinafter “IR light”) to a remote receiver that converts (e.g., demodulates) the IR light back into an audio signal and eventually back to reproducing the sound which is heard by a listener.
The LED emitters are typically low power, and an array of the LED emitters is typically required to provide enough IR light for the infrared audio system to work in a large area (e.g., conference room, auditorium, concert hall, outdoor venues, etc.). Conventional systems use LEDs that have a directional lens formed over the diodes of the LED emitters to focus the IR light in one general direction and to increase the power (e.g., amount and intensity of the light) emitted in that direction. A typical viewing angle of transmission (e.g., emitted light) from a single LED emitter used in such a conventional system is about 10° to 20° off center. Conventional systems use an array of these LED emitters that each have a narrow pattern (of IR light) such that the combined effect provides enough IR light for a receiver to be used at a practical distance from the LED emitters in many environments. A narrow pattern in conventional systems may work well for long and narrow rooms, but if a room is rectangular or square, the coverage area (e.g., area throughout which the infrared audio system emits IR light) provided by the infrared audio system on lateral sides of the room is poor in that there may be “dead zones” in which the IR signal may not be strong enough to produce the required signal for the receiver.
Wider viewing angles of transmission are available from some LED emitter manufacturers. However, due to the spreading of the IR light over a wider area, the number of LED emitters required to cover an entire area of a typical room is, in many cases, cost prohibitive. For example, a common approach used in the industry to attempt to increase the coverage area has been to use multiple (identical) infrared audio systems and point the infrared audio systems in different directions to get adequate coverage. This approach has the potential to cause gaps in coverage due to the IR light from the different infrared audio systems arriving out of phase (e.g., having latencies) with respect to each other and cancelling out the signal in certain locations within the room. Such cancelations may also cause dead zones within the room. In addition, requiring the user to purchase a large number of conventional systems with a coverage area having a single narrow pattern may increase costs—particularly for large areas. Other conventional approaches include changing the direction that the individual LED emitters point when mounted on the circuit board of the transmitting apparatus. In other words, one group points straight forward, while other groups of the array of LED emitters points outward at different angles in order to widen the combined coverage area emitted from the IR transmitter. In each group, however, the LED emitters are identical in terms of their individual lenses and emitting characteristics. Mounting the LED emitters in the array to point in different directions may add cost to the manufacturing process as well as difficulty in precision when the mounting occurs.